Recordings can be identified by physically encoding the recording or the media storing one or more recordings, or by analyzing the recording itself. Physical encoding techniques include encoding a recording with a “watermark” or encoding the media storing one or more audio recordings with a TOC (Table of Contents). The watermark or TOC may be extracted during playback and transmitted to a remote database which then matches it to supplemental content to be retrieved. Supplemental content may be, for example, metadata, which is generally understood to mean data that describes other data. In the context of the present invention, metadata may be data that describes the contents of a digital audio compact disc recording. Such metadata may include, for example, artist information (name, birth date, discography, etc.), album information (title, review, track listing, sound samples, etc.), and relational information (e.g., similar artists and albums), and other types of supplemental information such as advertisements and related images.
With respect to recording analysis, various methods have been proposed. Generally, conventional techniques analyze a recording (or portions of recordings) to extract its “fingerprint,” that is a number derived from a digital audio signal that serves as a unique identifier of that signal. U.S. Pat. No. 6,453,252 purports to provide a system that generates an audio fingerprint based on the energy content in frequency subbands. U.S. Pat. No. 7,110,338 purports to provide a system that utilizes invariant features to generate fingerprints.
Storage space for storing libraries of fingerprints is required for any system utilizing fingerprint technology to provide metadata. Naturally, larger fingerprints require more storage capacity. Larger fingerprints also require more time to create, more time to recognize, and use up more processing power to generate and analyze than do smaller fingerprints.
What is needed is a fingerprinting technology which creates smaller fingerprints, uses less storage space and processing power, is easily scalable and requires relatively little hardware to operate. There also is a need for technology that will enable the management of hundreds or thousands of audio files contained on consumer electronics devices at home, in the car, in portable devices, and the like, which is compact and able to recognize a vast library of music.